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When upsampling, factor is set to 1 and sines need to be evaluated only once for each phase, and the complexity should not depend on the number of filter taps. This does the desired precomputation, yielding significant speedups. Hard guarantees on the gain are not possible, but gains themselves are obvious and are illustrated below. Sample benchmark (x86-64, Haswell, GNU/Linux) test: fate-swr-resample-dblp-2626-44100 old: 29161085 decicycles in build_filter (loop 1000), 256 runs, 0 skips 28821467 decicycles in build_filter (loop 1000), 512 runs, 0 skips 28668201 decicycles in build_filter (loop 1000), 1000 runs, 24 skips new: 14351936 decicycles in build_filter (loop 1000), 256 runs, 0 skips 14306652 decicycles in build_filter (loop 1000), 512 runs, 0 skips 14299923 decicycles in build_filter (loop 1000), 1000 runs, 24 skips Note that this does not statically allocate the sin lookup table. This may be done for the default 1024 phases, yielding a 512*8 = 4kB array which should be small enough. This should yield a small improvement. Nevertheless, this is separate from this patch, is more ambiguous due to the binary increase, and requires a lut to be generated offline. Reviewed-by: Michael Niedermayer <michael@niedermayer.cc> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
FFmpeg README
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
Libraries
libavcodecprovides implementation of a wider range of codecs.libavformatimplements streaming protocols, container formats and basic I/O access.libavutilincludes hashers, decompressors and miscellaneous utility functions.libavfilterprovides a mean to alter decoded Audio and Video through chain of filters.libavdeviceprovides an abstraction to access capture and playback devices.libswresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
- ffplay is a minimalistic multimedia player.
- ffprobe is a simple analysis tool to inspect multimedia content.
- ffserver is a multimedia streaming server for live broadcasts.
- Additional small tools such as
aviocat,ismindexandqt-faststart.
Documentation
The offline documentation is available in the doc/ directory.
The online documentation is available in the main website and in the wiki.
Examples
Coding examples are available in the doc/examples directory.
License
FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.
Contributing
Patches should be submitted to the ffmpeg-devel mailing list using
git format-patch or git send-email. Github pull requests should be
avoided because they are not part of our review process. Few developers
follow pull requests so they will likely be ignored.